DUI lawyers often use medical and scientific evidence to challenge the prosecution’s case, especially when the defense revolves around questioning the reliability of the evidence or the defendant’s actual level of impairment. Here are several strategies DUI lawyers use to present such evidence:

1. Challenging Breathalyzer and Blood Test Accuracy

• Questioning Calibration and Maintenance: Fredericksburg DUI lawyer may argue that breathalyzer machines were not properly calibrated or maintained. They can request maintenance records to show that the equipment used to measure blood alcohol concentration (BAC) may have provided inaccurate results.
• Raising Doubts About Test Conditions: Lawyers may claim that external factors (such as the environment or the defendant’s health) affected the accuracy of the breath or blood test results. For example, conditions like acid reflux, diabetes, or even mouthwash can lead to falsely elevated BAC readings.
• Improper Test Administration: The lawyer can argue that the officer administering the breathalyzer or blood test did not follow proper procedures, which may invalidate the results. For example, a failure to observe the defendant for the required amount of time before conducting the test can be a point of contention.

2. Presenting Medical Conditions

• Health Conditions Mimicking Impairment: DUI lawyers can use medical evidence to show that the defendant has a condition (like diabetes, a neurological disorder, or anxiety) that may have caused symptoms resembling impairment, such as slurred speech or unsteady movement, but without actual intoxication.
• Absorption and Elimination Rates: In some cases, the lawyer may present evidence that the defendant’s body metabolizes alcohol differently, leading to skewed BAC results. Expert witnesses can explain how factors like body weight, gender, or metabolism rate could affect BAC at the time of the arrest versus when the test was administered.

3. Using Toxicology Experts

• Expert Testimony: Fredericksburg DUI lawyer often call upon toxicologists or medical experts to testify about the reliability of breath, blood, or urine tests. These experts can provide scientific analysis to explain how the defendant’s BAC level might not reflect impairment or how the test results could have been affected by improper handling or contamination.
• Prescription Medications: If the DUI involves prescription medications, a toxicology expert can explain how the effects of these medications might not equate to actual impairment. They may show that the dosage or side effects were not enough to render the defendant unfit to drive.

4. Challenging Field Sobriety Tests

• Scientific Reliability: DUI lawyers may argue that field sobriety tests, like walking in a straight line or the horizontal gaze nystagmus test, lack scientific reliability in determining impairment. Medical or scientific evidence can be used to demonstrate that factors such as fatigue, nervousness, poor balance, or pre-existing medical conditions could cause a person to fail these tests, even if they weren’t impaired.
• Conditions During the Test: Lawyers can also argue that environmental conditions, such as uneven surfaces, poor lighting, or inclement weather, may have contributed to poor performance on field sobriety tests, unrelated to impairment.

5. Blood Alcohol Content (BAC) Rising After Arrest

• Retrograde Extrapolation: DUI lawyers can use medical or scientific experts to argue that the defendant’s BAC may have been below the legal limit while they were driving but rose after the arrest due to alcohol still being absorbed into the bloodstream. This is called “rising BAC,” and experts can explain how the timing of alcohol consumption could impact the test results.

6. Chain of Custody Issues

• Contamination or Tampering: Fredericksburg DUI lawyer can challenge the chain of custody for blood or urine samples, arguing that the samples were not properly handled, stored, or transported. This can raise doubt about the accuracy of the test results, potentially leading to their exclusion from evidence.

7. Introducing Reasonable Doubt

• Questioning the Prosecution’s Evidence: By presenting scientific and medical evidence that highlights inconsistencies or potential errors in the prosecution’s case, DUI lawyers aim to create reasonable doubt. This can weaken the prosecution’s claim of impairment, leading to reduced charges or a dismissal.

Conclusion

DUI lawyers use medical and scientific evidence to challenge the prosecution’s case by questioning the accuracy of tests, presenting alternative explanations for observed behavior, and using expert testimony to undermine claims of impairment. This approach helps to create reasonable doubt, providing a strong defense for the defendant.